Electronic cigarettes may not shut off the urge to smoke cigarettes. A survey of 949 smokers found no difference in quit rates a year after some had taken up e-cigarettes while others hadn’t, researchers at the University of California, San Francisco report March 24 in JAMA Internal Medicine.

E-cigarettes deliver nicotine in vapor form without the cancer-causing combusted materials of a lit cigarette. Manufacturers suggest that using them is a first step toward quitting smoking. Of 949 smokers who answered online questionnaires, 88 reported trying e-cigarettes at the study’s outset. One year later, about 13.5 percent of all participants had quit smoking during the year. Roughly equal percentages of e-cigarette users and smokers who didn’t use them had successfully quit regular cigarettes; differences in quit rates between the two groups fell within the study’s margin of error.

Separately, studies published in 2013 in the Lancet and the American Journal of Preventive Medicine similarly found no more quitting among smokers who took up e-cigarettes. The UCSF authors suggest that regulators prohibit ads claiming that e-cigarettes help people quit smoking unless scientific evidence emerges to prove it.